I married on 11/28/2008 to a man while in jail. for my 2009-2010 tax return i''ve filed as single head of hous?

e hold. i checked on turbo tax to see whether there is a difference in my refund when filing married jointly and there is a difference. should i amend my taxes or should i change filing status next year. if i change my filing status do i have to change with my employer(w-4)form.